Electric incandescent lamp.



M. ARON & W. KEPPEL.

ELECTRIC INCANDEYSCENT LAMP.

APPLICATION FILED DEC.I9. ma.

1131. Patented Mar. 26, 1918.

WW I MBARON KE'PPEL MANFRED ARON, OF CHARLOTTENBURG, NEAR BERLIN, AND WILHELM KEPPEL, OF

BERLIN, GERMANY, ASSIGNORS TO THE FIRM OF PROGRESS, MOTOREN- UND APPA- BATENEAU G. M. B. 11., 0F GHARLO'ITENBURG, NEAR BERLIN, GERMANY.

ELECTRIC INGANDESCENT LAMP.

Specification of Letters Patent.

Patented Mar. 26,1918.

Application filed December 19, 1913. Serial No. 807,705.

To all whom it may concern:

; Be it known that we, MANFRED Anon, managing director, residing at Charlottenburg, near Berlin, Germany, and WILHELM Ker- PEL, engineer, residing at Berlin, Germany, both citizens of Germany, subjects of the King of Prussia and Emperor of Germany, have invented new and useful Improvements in and Relating to Electric Incandescent Lamps, of which the following is a specification.

This invention relates to electric incandescent lamps of the kind inwhich the luminous filaments or glowers or portions thereof are arran ed in a definite shape or form for ad vertislng or other purposes.

Ihe mvention relates more particularly to incandescent lamps of which the filaments or glowers represent letters, numbers, signs, words or pictures of any desired description and has for its object to overcome certain dificulties hitherto experienced in the construction and use of such lamps.

Adiflicultyin connection with lampsof this character is the reflectionv of light fromthe surfaces of the lamp which, while not objectionable in lamps employed for ordinary illumination, causes a want of distinctness and clearness inthe case of lamps of the kind to which the invention relates.

According to the present invention the imroved lamps are so constructed that ob- Jectionable reflections from portions of the lamp bulb are obviated.

The invention is illustrated in the accompanying drawings of which Figures 1 and 2' are views in side elevation of incandescent lamps constructed in accordance with the invention, Fig. 3 being a similar view but illustrating .a number of lamps connected in circuit with one another together with compensating resistances which will be hereinafter described.

Fig. 4 is a transverse sectional view of one of the lamps shown in Fig. 3.

In order to enable the lamps to be connected in circuit with one another and interchanged, each of the lamp filaments is arranged to have the same electrical res1stance, any variation in the length of the filaments being compensated for by an additional resistance forming a part of the internal circuit of each lamp. This additional resistance may be constituted by resistance wires or members and may be of any desired form or construction. In the arrangement shown in Fi 1 the additional resistance is located within the lamp bulb itself the filament of the lamp, which is of definite len h and form being indicated at a and the a diti-onal resistance indicated at 0 being located within the interior of a hollow container composed for instance of glass indicated at b.

In the modified arrangement illustrated in Fig. 2 the additional resistance is located as indicated at c in the portion of the bulb adbe obtained by locating the compensating resistance at any suitable point within the lamp bulb and arranging a non-transparent screen in front of the resistanceor an external screen may be provided covering the resistances of a group of lamps constituting an illuminated sign. In these cases the resistances may be of such nature or arranged under suchconditions, that they when the lamps are at work.

In a particularly simple construction of the lamp the. filament or glower is'made of greater length than is actually required by the form of the letter, sign or number to be represented, the portions of the filament not required to be visible being shielded or screened in any suitable manner. An arrangement of this kind is illustrated in Fig. 3 of the drawings, the left hand lamp of which represents the letter J, the portion 71 of the lamp filament a being covered or surrounded by an opaque casing or screen la so that this portion of the filament is invisible to the observer; this portion of the filament may be used for throwing light in another direction. It will be readily underst that n h m nn r lamp represents are glowing ing different letters or numbers may be constructed having filaments of equal length so that the resistance of each lamp is the same and they can consequently be interchanged or connected together without difficulty.

From the above description it will be understood that a number of lamps, each representing a different letter, number or the like, may be connected together in series so as to represent words or combinations of numbers and in such cases the number of lamps required in a single series group may be insufficient for the supply circuit voltage. I11 order to remedy this defect additional resistances are provided each corresponding to the resistance of one or more of the individual lamps these resistances being provided with lamp caps and sockets 1n the ordinary form so that oneor more of these resistances can be connected in a serles group containing the lamps representing the letters or signs required. The additional resistances may be in the form of lamps the whole of the filament of which is invisible to the observer or may be constituted by non-luminous resistances.

A series group of the kind above described is illustrated in Fig. 3 of the drawings in which two lamps representing the letters J A are connected in series with two additional resistances necessary to complete the total resistance of the circuit necessary for the voltage supply available. It will thus be seen that the two additional resistances shown on the right hand side of the figure replace two lamps which will be utilized in the event of a word of four letters having to be represented. In the case of one of these additional resistances the resistance body a is arranged in a suitable lamp bulb or container e and is provided with a; lamp cap at of the usual type. The other additional resistance at the extreme righthand of the drawing comprises a lamp bulb of the usual form inclosing the resistance wire 0 which is Zi)nclosed in an opaque casing indicated at In order to insure that the letter or figure or the like represented by the filament or glower shall always directly face the observer, the central contact of the lamp ca or the contact plate of the lamp holder 1s arranged to be resilient so that an efi'ective electrical connection is made before the lamp bulb is completely screwed into position in the holder. The lamp can therefore be rotated through a considerable range without being disconnected from the supply circuit and its position can be adjusted so that the filament or glower occupies the desired plane.

In case of the lamp representing the letter J in Fig. 3, the central contact of the lamp cap d is provided with a spring projection is forming a resilient contact member. The portions of the lamp filament forming the letter in question are mounted upon a suitably formed glass stem or carrier 7 tO'WhlCl] the filament is attached by means of supporting wires g. The compensating reslstances or non-luminous part of the filament portion of the stem or carrier 7.

In the case of the other lamp representing the letter A, the compensating resistance indicated at c is located within the ca of the lamp and the internal contact of t e lamp holder h is in this case provided with a resilient extension or projection.

In order to prevent objectionable reflections from the lamp bulb the portions of the latter which are so situated as to cause such reflection, are according to the present in-.

vention constructed of ground glass, for instance the portion of the wall of the bulb behind and on each side of the filament or glower, the stem or carrier for the filament and the cover or casing of the resistance are obscured in this way by utilizing any suitable method for the purpose, such for instance as treatment with corrosive material, a sand blast or other suitable means.

As will be readily understood, it is particularly necessary to treat the inner portions of the glass bulb and the carrier of the filament or glower in this manner and the corresponding outer surface of this portion of the bulb can if desired also be frosted, ground or constructed of dark colored glass having a mat surface. The effect of the luminous filaments is also enhanced if in addition to frosting or coating the internal surface of the lamp bulb behind the filament, the corresponding external surface 'of the bulb is provided with a dark coating by the application for instance of black varnish, in which case the portion of the lamp bulb behind the filament appears to have a dark mat surface so that the luminous filament stands out clearly from this background and presents the letter, number or the like in a particularly efiective manner.

The glass stem or carrier may evidently be similarly treated for obtaining the same purpose.

In Figs. 3 and 4 of the drawings the port1ons of the lamp thus treated are indicated in hatched lines and as will be seen from Fig. 4, the rear half of the lamp bulb is thus treated as well as the stem or carrier f.

The invention is evidently not limited to the precise construction and details above described which can be modified to meet particular conditions.

aving now described our invention what we claim and desire to secure by Letters Patent of the United States is:

1. An electric incandescent lamp, in which is located in an opaque casing b forming a the carriers for the filament are rendered set our hands in presence of two subscribing V non-reflecting. witnesses.

2. An electric incandescent lamp in which the internal surface of the bulb behind the 5 filament is rendered non-reflecting, and the corresponding external surface of the bulb Witnesses: is rendered dark mat. WOLDEMAR HAUPT,

In testimony whereof We have hereunto HENRY HASPER. 

